If you do USB printer sharing, please tell us what printer or all-in-one you've tried sharing via OSX printer sharing and whether you could share it without anyone being logged in. I'll start, to provide a template:
HP 5150 -- works even logged out
Lexmark X83 -- only works if logged in
Cheapo P22 -- never works shared
For those of us in the market for a new printer that we want to share (I have a bunch of X83's I need to replace), this information would be very useful. And the manufacturers aren't going to tell you this important subtlety.
As to the issue here... with some printers, if nobody is logged into the sharing machine, then the print jobs just queue up until someone logs into it. With other printers, the jobs run just fine whether someone is logged in or not. Good driver vs. bad driver.
Thanks!